Blow molding machine

ABSTRACT

A blow molding machine designed as a two station machine (10) has at least one extrusion device (12) and an accumulator head which supplies a tubular thermoplastic parison to two blow molds arranged next to each other and having two horizontally movable blow molding halves. In order to simplify the construction of the machine at reduced space and to achieve a high productivity, the blow molding machine according to the invention has only a three-platen system with three mold mounting plates (22, 24, 26) for clamping the four blow molding halves (14, 16, 18, 20).

BACKGROUND OF THE INVENTION

The invention refers to a blow molding machine designed as two-stationmachine including at least one extrusion device, possibly withaccumulator head, which supplies a tubular thermoplastic parison to twoblow molds arranged next to each other and having two horizontallymovable blow mold halves, and a machine frame upon which the two blowmolds or four blow mold halves are slidably supported.

Such a two-station blow molding machine is generally known per se. Theknown machine is provided with a complex encircling frame structure withfour bars and additional external support of the drive unit asfive-platen-system. This incurs significant initial costs, requires aneed for large space and necessitates a complicated control of twoseparate closing devices.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an efficienttwo-station blow molding machine which enables a high productivity atlow initial costs and operating expenses and at reduced demand forspace. In accordance with the invention, this object is attained byproviding only one three-platen system with three mold mounting platesfor clamping the four blow mold halves, with one blow mold half of eachof both blow molds being affixed to the central mold mounting plate. Thecentral mold mounting plate thus carries one blow mold half on each sideto the right and to the left.

A proper handling of the machine with unrestricted product removalcapability and no obstructing cross bars is advantageously attained bydesigning the machine frame only in form of a table which is exclusivelyarranged underneath the blow mold halves and mold mounting plates. Thehorizontal movement and rapid feed-closing movement of both blow moldhalves is thereby provided in an amazingly simple manner by only onesingle driving cylinder, the piston rod of which is mounted at bothsides to the machine frame while the final locking motion of therespective blow mold halves to their final locking position is effectedby providing each mold mounting plate with separate locking unitscomprised of small locking cylinders with opposing locking pins. Forsmaller products like e.g. a 10I canister, it is sufficient to providein the center of a respective blow mold at half height two neighboringclosing cylinders with locking pins (as shown in the drawings). Forlarger blow molding products (e.g. a 220 I drum) and at larger blowingpressures and prevailing forces, all four corner areas of each moldmounting plate are provided with the respective closing cylinders andlocking pins.

In accordance with an embodiment of the invention, the single drivingcylinder is operatively connected with the respective blow mold halvesto be actuated via a coupling, preferably in form of a hydrauliccylinder with pinion engageable and shiftable in the racks of thesynchronizing devices. Thus, in a most simple way, a 2-station blowmolding machine can be made available with an operationally advantageousmotion system.

The three-platen system according to the invention provides thefollowing advantages:

open, frameless structure, lack of heavy frame construction since aclosed power system is respectively provided within each mold mountingplate;

targeted introduction of the closing forces into the blow mold halves,

no disturbing cross beams or bars e.g. at product removal, moldreplacement or repair works,

small structural units with slightly moving masses, thus requiring smallforces at fast feed motions,

slight wear of moving parts,

minimization of the number of components,

compact structure,

mobility of the entire arrangement,

minimization of the machine size and demand on space required in theproduction hall,

increase of the productivity at reduced investment,

easy handling (control) of the machine,

low operational costs and

possibility of a simultaneous production of two different products,

A particular feature is the complete mobility of the entire two-stationblow molding machine, for example via rails in the foundation and wheelsunderneath the base frame of the machine. Suitably, the moving wheelsfor the entire machine unit are equipped with a separate drive motor.This embodiment is in particular very advantageous when replacing moldsor dies because the accessibility is considerably improved.

BRIEF DESCRIPTION OF THE DRAWING

The invention is now explained and described in more detail withreference to an exemplified embodiment illustrated in the drawings, inwhich

FIG. 1 shows a two-station blow molding machine according to theinvention,

FIG. 2, 3 and 5-9 show various positions of a two-station blow moldingmachine,

FIG. 4 shows a schematic illustration of the synchronizing device of theblow molding machine and

FIG. 10 a view of the blow molding machine upon dismantling of a blowmold.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In FIG. 1, reference numeral 10 designates a two-station blow moldingmachine according to the invention with a three-platen system formounting four blow mold halves 14, 16; 18, 20. Indicated centrally abovethe blow molding machine 10 is an extrusion device 12 which supplies atubular parison of thermoplastic material, extruded from a die ring, totwo neighboring horizontally slidable blow molds for blowing hollowplastic bodies such as e.g. canisters, large volume drums (lidded drums,bunged drums or the like). The tubular parison may e.g. also be extrudedcontinuously to enable a continuous operation. In a discontinuedoperation, the tubular parison is ejected intermittently from theextrusion device with respective accumulator head.

The four blow mold halves 14, 16 and 18, 20 are affixed in easilydetachable manner and mounted to three mold mounting plates 22, 24 and24, 26, with the central mold mounting plate 24 carrying on the frontside and back side a respective blow mold half 16 and 18. The three moldmounting plates 22, 24, 26 are supported for horizontal displacement viaplatforms 28, 30, 32 on a base machine frame which is formed as flattable 34. In contrast to conventional two-station blow molding machines,the base machine frame in form of a table 34 is arranged exclusivelyunderneath the blow molds and platforms 28, 30, 32 of the mold mountingplates 22, 24, 26 for mounting and clamping the blow mold halves 14, 16;18, 20. The platforms 28, 30, 32 are guided for displacement by e.g.rollers on rails or guide bars arranged laterally of the table 34. Bothouter mold mounting plates 22 and 26 are each further propped via anexternal support 36, 38 on both outer platforms 28 and 32. For guidingthe platforms 28, 30, 32 and the pertaining blow mold halves insynchronism, two small hydraulic centering cylinders 58 are providedcentrally underneath each blow mold. The hydraulically centeringcylinders 58 are arranged e.g. laterally next to the blow mandrel device60 which is also arranged always centrally in the mold parting plane, asindicated in FIG. 1. At normal operation, only one gear 50 is ineffective engagement by means of the respective centering cylinder 58.The centering cylinders 58 of the synchronizing guide system areoperatively connected to the synchronizing device 44, with thesynchronizing device 44 including e.g. a rack and pinion system with aright and a left rack 40, 42 and 46, 48 and an interposed gear 50 orpinion, as schematically illustrated in FIG. 4. One rack 40, 42 and 46,48 is thereby securely fixed to one mold mounting plate 22 and 24; 24and 26, respectively. Both racks may certainly be arranged alsoabove/below each other.

Through actuation of the centering cylinders, the gear 50 of thesynchronizing device 44 engages for example both racks 46, 48 or is idlethrough displacement (disengagement). The horizontal movement and rapidclosing movement (rapid feed) of both blow mold halves 14, 16 and 18, 20is effected only by a single hydraulic driving cylinder 52 which isarranged centrally on the table 34 and is connected and coupled with thedownwardly extended central platform 30. Thus, the driving cylinder 52directly moves only the central platform 30 with the central moldmounting plate 24 and both blow mold halves 16, 18 affixed thereto. Theouter blow mold half 14 or 20 of the respectively closed blow mold isthereby coupled by its own separate locking unit to the inside blow moldhalf 16 or 18 while the centering cylinder of the closed blow moldrenders the synchronizing device idle. At open blow mold, thesynchronizing device is operated through engagement of the pinion bymeans of the centering cylinder, and the movement of the driven insideblow mold half 16 or 18 (via mold mounting plate 24 and platform 30 anddriving cylinder 52) is effected relative thereto by the opposingoutside blow mold halves 14 or 20 also in opposite direction. The finallocking motion of the respective blow mold halves 14, 16 and 18, 20 intotheir locking position is effected by separate locking units comprisedof a small closing cylinder 54 with opposing locking pin 56 andrespectively arranged on the mold mounting plates 22, 24, 26. A blowmandrel device 60 with respective expanding mandrel and blow mandrel isarranged on the table 34 centrally underneath each blow mold. Expandingmandrel and blow mandrel are movable relative to each other in a knownmanner, that is moved together for attachment of the parison and movedapart during closing of the blow mold halves. It is in particularnoteworthy regarding the drive of the blow mold halves by means of thedriving cylinder 52, that the piston rod is fixedly secured in the frameon both sides and the driving cylinder 52 as moving pad travelshydraulically along the fixed piston rod.

The table 34 stands on two or here three legs 62. In accordance with apreferred embodiment, the legs 62 are equipped on their lower extremitywith rollers or wheels 64 and the entire blow molding machine 10 travelsor is movable on rails 66 or other means. In order to effect thedisplacement of the entire arrangement, the wheels 64 may be providedwith a particular linear drive (e.g. electromotor).

The mode of operation of the two-station blow molding machine is evidentfrom the following drawings: In accordance with the new control concept,at operation of the machine one station is always closed while the otherstation is shifted or moved. In FIG. 2, the right station is closedwhile both blow mold halves 14, 16 of the left station are completelyopen. After ejecting the tubular parison 68 from the extrusion device 12and the spreading of the tube by means of the expanding mandrel and blowmandrel of the blow mandrel device 60, the rapid closing of the leftstation is effected until reaching the position "inching". This iseffected by means of the centrally arranged hydraulic driving cylinder52 underneath the blow mandrel device 60. Two small hydraulic centeringcylinders 58 arranged centrally and in the blow mold parting line nextto the blowing mandrel device 60 maintain the synchronizing guidesystems in position. The synchronized guide systems operate e.g.according to the conventional rack and pinion system. As soon as theposition "inching"--illustrated in FIG. 3--is reached, the closingcylinders 54 and locking pins 56 arranged on the mold mounting plates 22and 24 assume the retarded locking motion while pinching off the tubeunder great force application and hold the blow mold closed against theprevailing blowing pressure. As shown in FIG. 5, both stations are nowclosed. After releasing both centering cylinders 58, both stations,which are supported by the platforms 28, 30, 32 for rolling upon thetable 34, are positioned by the driving cylinder 52 in such a mannerthat the right station now stops again underneath the accumulator head12, as shown in FIG. 6. The centering cylinders secure thereby thesynchronizing guide system. After elapse of the blowing time and releaseof the locking units, the right station is opened by means of thedriving cylinder for allowing a removal of the finished blow moldedhollow body, as shown in FIG. 7. As soon as the blown hollow body, herea canister, is removed from the blow mold, a new tubular thermoplasticparison is again ejected from the die ring of the extrusion device 12,and the further operation proceeds in a same manner as previouslydescribed in connection with the left station.

In order to improve the accessibility e.g. for maintenance purposes, thenormal operational opening distance until the "opening position" of bothmold halves can be significantly increased. In this case, both centeringcylinders 58 are idle. Through selective actuation of the drivingcylinder 52, the left station--as illustrated in FIG. 8--or the rightstation--as illustrated in FIG. 9--can be opened even further to a"maintenance position". A precondition for that is a correspondinglength of the rails for the platforms. As best seen from FIG. 10, theentire two-station blow molding machine unit is movable together withthe lower base frame 34. This is effected e.g. via rails 66 in thefoundation and wheels 64 underneath the legs 62 of the base frame 34.This is especially advantageous when replacing one blow mold or e.g.during a change of dies in the extrusion device 12. In FIG. 10, the twoblow mold halves 18, 20 of the right station are about to be dismantledby means of a crane hook, with the blow mold machine unit being movedout from underneath the extrusion device 12. The mobility of the blowmold machine unit could e.g. also be utilized to alternately positionthe blow molds underneath two neighboring extrusion dies and accumulatorheads. In principle, the two-station blow molding machine could be usedto simultaneously produce two different types of hollow bodies, e.g. a60 I barrel with lateral drop handles in the left station and a 60 Istandard lidded drum in the right station. However, also randomcontainer shapes even with different container size (e.g. 150 I conicallidded drum and a 160 I bunged drum) can be produced simultaneously withthe new blow molding machine. When equipping the plant with a secondextruder or accumulator head, also containers of different colors ordifferent plastic material could be blown.

Above description and drawings clearly illustrate the advantageousembodiment of the two-station blow molding machine according to theinvention with new three-platen system.

LIST OF REFERENCE NUMERALS

10 two-station machine

12 extrusion device

14 blow mold half-left station

16 blow mold half-left station

18 blow mold half-right station

20 blow mold half- right station

22 left mold mounting plate

24 central mold mounting plate

26 right mold mounting plate

30 central platform

32 right platform

34 table (base frame)

36 left mold mounting plate support

38 right mold mounting support

40 upper rack (right station)

42 lower rack (right station)

44 synchronizing device

46 upper rack (left station)

48 lower rack (left station)

50 gear (pinion)

52 moving cylinder

54 closing cylinder

56 locking pin

58 centering cylinder for (44)

60 blow mandrel device

62 frame legs

64 roller (wheels)

66 rails

68 plastic parison

We claim:
 1. A blow molding machine in form of a two-station machine,comprising:an open machine frame; a pair of blow molds arranged next toeach other and each being split to define two blow mold halves; clampingmeans mounted on said machine frame for supporting said blow mold halvesduring movement in a horizontal direction, said clamping means being athree-platen system with three mold mounting plates, with a central moldmounting plate thereof supporting one blow mold half of each blow mold;support means movably mounted on said machine frame for individuallysecuring each of said mold mounting plates to said machine frame andallowing movement of said mold mounting plates separately from eachother in horizontal direction; and at least one extrusion meanssupplying a tubular thermoplastic parison to said blow molds.
 2. Theblow molding machine of claim 1 wherein said machine frame is formed asa table which is exclusively arranged underneath the blow mold halvesand mold mounting plates, and further comprising rails laterally securedon said table for guiding said support means during movement thereof. 3.The blow molding machine of claim 1, and further comprising a drivemeans formed with one single driving cylinder operatively connected tothe central mold mounting plate for effecting a horizontal movement ofsaid blow mold halves.
 4. The blow molding machine of claim 3, andfurther comprising a coupling unit for operatively connecting saiddriving cylinder with said blow mold halves.
 5. The blow molding machineof claim 4 wherein said coupling unit includes a hydraulically actuatedcentering cylinder formed with a pinion for cooperation with a rackassembly secured to said mounting plates, with said pinion beingengageable in said rack assembly through actuation of said centeringcylinder.
 6. The blow molding machine of claim 1 wherein each said blowmolds is provided with a separate locking mechanism formed with a smalllocking cylinder secured to one mounting plate and an opposing lockingpin secured to the central mounting plate for effecting a final lockingmotion of said blow mold halves into the final locking position.
 7. Theblow molding machine of claim 6 wherein under normal operationalconditions one of said blow molds is closed and locked by the respectivelocking mechanism while the other one of said blow molds is open, withits blow mold halves executing a closing or opening motion, whereby saidone blow mold on one side of said central mold mounting plate followsthe movement of said blow mold half on the other side of said centralmold mounting plate through coupling via said common central moldmounting plate.
 8. The blow molding machine of claim 1 wherein said blowmold halves are movable beyond a normal operational opening position toan even further opened maintenance position.
 9. The blow molding machineof claim 1, further comprising a separate drive for moving the entiretwo station machine together with said machine frame.